<?php
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP
 *
 * This content is released under the MIT License (MIT)
 *
 * Copyright (c) 2014 - 2015, British Columbia Institute of Technology
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @package    CodeIgniter
 * @author    EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
 * @license    http://opensource.org/licenses/MIT    MIT License
 * @link    http://codeigniter.com
 * @since    Version 2.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * CodeIgniter File Caching Class
 *
 * @package        CodeIgniter
 * @subpackage    Libraries
 * @category    Core
 * @author        EllisLab Dev Team
 * @link
 */
class CI_Cache_file extends CI_Driver {

    /**
     * Directory in which to save cache files
     *
     * @var string
     */
    protected $_cache_path;

    /**
     * Initialize file-based cache
     *
     * @return    void
     */
    public function __construct()
    {
        $CI =& get_instance();
        $CI->load->helper('file');
        $path = $CI->config->item('cache_path');
        $this->_cache_path = ($path === '') ? APPPATH.'cache/' : $path;
    }

    // ------------------------------------------------------------------------

    /**
     * Fetch from cache
     *
     * @param    string    $id    Cache ID
     * @return    mixed    Data on success, FALSE on failure
     */
    public function get($id)
    {
        $data = $this->_get($id);
        return is_array($data) ? $data['data'] : FALSE;
    }

    // ------------------------------------------------------------------------

    /**
     * Save into cache
     *
     * @param    string    $id    Cache ID
     * @param    mixed    $data    Data to store
     * @param    int    $ttl    Time to live in seconds
     * @param    bool    $raw    Whether to store the raw value (unused)
     * @return    bool    TRUE on success, FALSE on failure
     */
    public function save($id, $data, $ttl = 60, $raw = FALSE)
    {
        $contents = array(
            'time'        => time(),
            'ttl'        => $ttl,
            'data'        => $data
        );

        if (write_file($this->_cache_path.$id, serialize($contents)))
        {
            chmod($this->_cache_path.$id, 0640);
            return TRUE;
        }

        return FALSE;
    }

    // ------------------------------------------------------------------------

    /**
     * Delete from Cache
     *
     * @param    mixed    unique identifier of item in cache
     * @return    bool    true on success/false on failure
     */
    public function delete($id)
    {
        return file_exists($this->_cache_path.$id) ? unlink($this->_cache_path.$id) : FALSE;
    }

    // ------------------------------------------------------------------------

    /**
     * Increment a raw value
     *
     * @param    string    $id    Cache ID
     * @param    int    $offset    Step/value to add
     * @return    New value on success, FALSE on failure
     */
    public function increment($id, $offset = 1)
    {
        $data = $this->_get($id);

        if ($data === FALSE)
        {
            $data = array('data' => 0, 'ttl' => 60);
        }
        elseif ( ! is_int($data['data']))
        {
            return FALSE;
        }

        $new_value = $data['data'] + $offset;
        return $this->save($id, $new_value, $data['ttl'])
            ? $new_value
            : FALSE;
    }

    // ------------------------------------------------------------------------

    /**
     * Decrement a raw value
     *
     * @param    string    $id    Cache ID
     * @param    int    $offset    Step/value to reduce by
     * @return    New value on success, FALSE on failure
     */
    public function decrement($id, $offset = 1)
    {
        $data = $this->_get($id);

        if ($data === FALSE)
        {
            $data = array('data' => 0, 'ttl' => 60);
        }
        elseif ( ! is_int($data['data']))
        {
            return FALSE;
        }

        $new_value = $data['data'] - $offset;
        return $this->save($id, $new_value, $data['ttl'])
            ? $new_value
            : FALSE;
    }

    // ------------------------------------------------------------------------

    /**
     * Clean the Cache
     *
     * @return    bool    false on failure/true on success
     */
    public function clean()
    {
        return delete_files($this->_cache_path, FALSE, TRUE);
    }

    // ------------------------------------------------------------------------

    /**
     * Cache Info
     *
     * Not supported by file-based caching
     *
     * @param    string    user/filehits
     * @return    mixed    FALSE
     */
    public function cache_info($type = NULL)
    {
        return get_dir_file_info($this->_cache_path);
    }

    // ------------------------------------------------------------------------

    /**
     * Get Cache Metadata
     *
     * @param    mixed    key to get cache metadata on
     * @return    mixed    FALSE on failure, array on success.
     */
    public function get_metadata($id)
    {
        if ( ! file_exists($this->_cache_path.$id))
        {
            return FALSE;
        }

        $data = unserialize(file_get_contents($this->_cache_path.$id));

        if (is_array($data))
        {
            $mtime = filemtime($this->_cache_path.$id);

            if ( ! isset($data['ttl']))
            {
                return FALSE;
            }

            return array(
                'expire' => $mtime + $data['ttl'],
                'mtime'     => $mtime
            );
        }

        return FALSE;
    }

    // ------------------------------------------------------------------------

    /**
     * Is supported
     *
     * In the file driver, check to see that the cache directory is indeed writable
     *
     * @return    bool
     */
    public function is_supported()
    {
        return is_really_writable($this->_cache_path);
    }

    // ------------------------------------------------------------------------

    /**
     * Get all data
     *
     * Internal method to get all the relevant data about a cache item
     *
     * @param    string    $id    Cache ID
     * @return    mixed    Data array on success or FALSE on failure
     */
    protected function _get($id)
    {
        if ( ! file_exists($this->_cache_path.$id))
        {
            return FALSE;
        }

        $data = unserialize(file_get_contents($this->_cache_path.$id));

        if ($data['ttl'] > 0 && time() > $data['time'] + $data['ttl'])
        {
            unlink($this->_cache_path.$id);
            return FALSE;
        }

        return $data;
    }

}
